Camelbak Thermobak Omega Hydration Backpack Extra-wide, 1.75-inch/45mm opening can be filled with ice cubes for extra-cool hot weather hydrating HydroLock Valve provides positive shut off switch for anti-leak security Big Bite Silicone Valve releases more water when you need it Closed cell foam insulation keeps liquids cooler longer and does not absorb moisture or perspiration 1000 denier Cordura nylon shell and heavy duty, double-stitched construction